Name already in use

In the previous commit, the default value of the input is ${{ github.workspace }}
which means that most uses of this input would probably prefix their paths with
${{ github.workspace }}, especially since actions/checkout's 'path' input
must be under ${{ github.workspace }}. Therefore, it doesn't make much sense for
this to be an absolute file path.

Instead, it's more intuitive to make this relative to the repository.